QUANTIFICATION OF COMPLEX POLYCYCLIC AROMATIC HYDROCARBONS OR PETROLEUM OILS IN WATER WITH CARY ECLIPSE FLUORESCENCE SPECTROPHOTOMETER ACCORDING TO ASTM D 5412-93 (2000)

Importance of the topic

Quantifying polycyclic aromatic hydrocarbons (PAHs) and petroleum oils in water is critical for environmental monitoring, regulatory compliance and human health protection. These contaminants pose carcinogenic risks and require sensitive, selective analytical methods. The ASTM D5412 standard defines a fluorescence‐based approach for accurate measurement of complex PAH mixtures in aqueous samples.

Objectives and overview of the study

This study evaluated the performance of an Agilent Cary Eclipse Fluorescence Spectrophotometer to implement ASTM D5412-93 (2000). Key goals were:

• Test calibration, precision, limits of detection and quantification for individual PAH analytes (naphthalene, benzo[a]pyrene, anthracene).
  
• Compare pipetting approaches and optimize sample preparation.
  
• Assess method recovery for individual standards and mixed PAH solutions.
  

Used Instrumentation

• Agilent Cary Eclipse Fluorescence Spectrophotometer with quartz cuvettes (1 cm path length).
  
• Analytical balance (Ohaus Explorer Pro).
  
• Volumetric flasks (A-class borosilicate glass).
  
• Automatic pipettes (Eppendorf with Biopur tips), Hamilton microliter syringes.
  
• Millipore Milli-Q water system and HPLC-grade cyclohexane.
  
• Reagents: naphthalene, anthracene, benzo[a]pyrene standards, nitric acid.
  

Methodology

Sample and calibration solutions were prepared in cyclohexane according to ASTM D5412. Solvent and water blanks were evaluated to confirm <5% blank intensity. Calibration ranges:

• Naphthalene: 0.2–100 µg/mL at Ex 250 nm, Em 324 nm.
  
• Benzo[a]pyrene: 0.005–0.25 µg/mL at Ex 268 nm, Em 405 nm.
  

For each level, three replicate spectra were recorded. Slit widths were optimized to improve sensitivity. Limits of detection (LOD) and quantification (LOQ) were calculated using 3σ and 10σ criteria. Precision was divided into repeatability and day-to-day components by variance analysis.

Main Results and Discussion

Key performance data:

• Naphthalene (Ex 250 nm): LOD 0.13 µg/mL, LOQ 0.5 µg/mL; R²=0.9985.
  
• Naphthalene (Ex 268 nm): LOD 0.5 µg/mL, R²=0.9902.
  
• Benzo[a]pyrene (narrow slits): LOD 0.06 µg/mL, R²=0.9944.
  
• Benzo[a]pyrene (wider slits): LOD 0.005 µg/mL, R²=0.9984.
  
• Relative standard deviations were below 0.2 for low‐level replicates and improved at higher concentrations.
  
• Recoveries for individual PAHs ranged from 96% to 104%, within ASTM acceptance criteria.
  
• Mixed-PAH recoveries were within ±20% across 0.03–0.5 µg/mL total concentration.
  

Benefits and Practical Applications

The Agilent Cary Eclipse system meets ASTM D5412 requirements, offering:

• High sensitivity enabling sub-microgram detection of priority PAHs.
  
• Robust precision and accuracy for routine water quality analysis.
  
• Rapid, cost-effective workflow using standard lab accessories.
  

Future Trends and Potential Uses

Emerging developments may include:

• Integration with automated sample extraction and flow-through cells.
  
• Enhanced multiplexing for simultaneous detection of multiple PAHs.
  
• Application of chemometric methods to deconvolute complex mixtures.
  
• Miniaturized and portable fluorimetric systems for field monitoring.
  

Conclusion

The Cary Eclipse Fluorescence Spectrophotometer successfully implements ASTM D5412-93 for the quantification of PAHs in water. It delivers excellent sensitivity, precision, and recovery for both individual analytes and complex mixtures, providing a reliable solution for environmental and industrial laboratories.

References

• ASTM D5412-93 (2000) Standard Test Method for Quantification of Complex Polycyclic Aromatic Hydrocarbon Mixtures or Petroleum Oils in Water.
  
• ISO/IEC 17025:2005 General requirements for the competence of testing and calibration laboratories.
  
• IUPAC (1998) Recommendations for the presentation of results of chemical analysis.
  
• Doerffel K. Statistik in der analytischen Chemie. Leipzig: Deutscher Verlag; 1994.
  
• Bayrakceken F. Radiative electronic energy transfer studies of naphthalene–biacetyl. Spectrochim. Acta A. 2005;61(6):1069–74.
  
• Donaldson DJ et al. Uptake and reaction of atmospheric organic vapours on organic films. Faraday Discuss. 2005;130:227–39.